1. Field of the Invention
The present invention relates to tanks for storing and moving pulverulent or powdered material such as cement, drilling fluid additives such as barites, bentonite and the like, and pulverulent oil and gas well treatment materials used to increase production of oil wells by fracturing petroleum-containing geologic strata, and the like. In particular, the present invention is related to pneumatic tanks used for storing, transporting and discharging pulverulent material commonly used in petroleum and natural gas exploration and production.
2. Description of the Related Art
In the petroleum and natural gas exploration industry it is necessary to transport various pulverulent materials from onshore storage, manufacturing, mining, and storage facilities by barge or ship to marine inshore and offshore exploration and production locations. Some of these materials are very expensive, and many of the materials are difficult to unload from a ship or barge because the common gravity feed dump trucks used onshore cannot be utilized in a marine environment. Commonly, significant portions of these materials remain in the storage tank on the ship or barge in which they are transported due to difficulty encountered in removing all of the materials from the barge or other transport vessel at the marine production or exploration locations where the materials are being unloaded.
The storage and discharge tanks for pulverulent material of the prior art commonly are unable to discharge a large percentage of the material stored and transported in the tank. Such residue remains in the tank and travels with the tank back to the storage facility for the pulverulent material. The residue left in the tank greatly adds to the expense of transport and discharge of the pulverulent material.
Exemplary of the Patents of the related art are the following U.S. Pat. Nos.: 4,459,070; 4,088,373; 1,570,795; 1,759,983; 2,915,339; 2,965,269; 3,226,166; 4,846,377; 5,018,909; 5,031,546; WO55073A1 and JP56043130.
In accordance with the present invention there is provided a pneumatic storage tank for storing, transporting, and discharging pulverulent or powdered material or the like including a tank having a cylindrical side wall and upper and lower concave heads enclosing and sealing opposite ends of the cylindrical side wall, the tank adapted to be supported in a vertical position, a plurality of slope sheets within the tank, the slope sheets being sealed to the cylindrical side wall around the full circumference of the cylindrical side wall, the slope sheets being inclined downwardly from the cylindrical side wall to the central region of the tank adjacent the lower concave head of the tank, a plurality of air slides within the tank, the air slides disposed along the slope sheets between the slope sheets and extending from the cylindrical side wall of the tank downwardly toward the central region of the tank adjacent the lower concave head of the tank, wherein the slope sheets and the air slides separate the tank into an upper compartment and a lower compartment, an inlet pipe for providing the material to be stored therein into the upper compartment of the tank, a discharge pipe for removing the material from the upper compartment of the tank, the discharge line extending from a point adjacent to the slope sheets in the central region of the tank adjacent to the lower concave head of the tank, an air pipe positioned in the lower compartment of the tank, the air slides being adapted to release the air supplied thereto through the air slides into the upper compartment to suspend pulverulent material in the upper compartment, and an air nozzle located at the upper end of each of the air slides adjacent to the side wall of the tank, the air nozzle being adapted to direct air under superatmospheric pressure downward along the surface of the air slide to urge the pulverulent material downwardly from the side wall toward the central region of the tank.
The pneumatic tank of the invention has the advantage of rapid removal of pulverulent material therefrom.
The pneumatic tank of the invention has the further advantage of discharging substantially all of the pulverulent material stored and transported therein.